The present invention relates to a plate, and more particularly to a digital plate.
Conventional index input devices for the computer are generally categorized into two types:
1) The digital plate device 100, as shown in FIG. 1, includes an induction plate 101, an electronic pen 102 having a front coil 104 capable of generating a magnetic field of a low strength, and a controller 103. Induction plate 101 is a printed circuit board disposed therein metal rods 105 capable of inducing a current having a magnitude inversely proportional to the distance between metal rods (or wires) 105 and front coil 104 when electronic pen 102 comes close to induction plate 101. Thus, controller 103 can periodically read the current message of metal rods 105 to be converted into the actual coordinate position for pen 102 to be processed by the CPU 106 of a computer for accordingly moving the cursor in the monitor 107 of the computer.
Such type of index input device requires a special pen 102 so that it is relatively costly.
2) The mouse assembly 200, as shown in FIG. 2, includes 3 (or 2) functional keys L, M & F, a key detector 201, a movement detector 202 and a logic control device 203. Movement detector 202 has a counter and an optical coupler detecting the movement of mouse assembly 200 so that when assembly 200 moves, the optical coupler in detector 202 will generate a series of logic signals which have a frequency proportional to the moving speed of assembly 200 and trigger the counter to count until assembly 200 stops moving. What is recorded in the counter will be the coordinate movement of assembly 200. Whenever there is a movement of assembly 200 or a pressed functional key L, M or R, control device 203 will transmit in a specific format the key status and/or the movement of assembly 200 to be processed by CPU 106. Such type of index input device is now extensively used and is relatively cost-effective but can only provide 3 functional keys owing to the limited size of assembly 200 and cannot easily reach the corresponding position in monitor 107 as digital plate device 100 does so that it has limited control function and convenience in use.
It is therefore attempted by the applicant to deal with the shortcomings encountered by the prior art.